852
FXUS65 KBYZ 092339
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
539 PM MDT MON MAR 9 2026
KEY MESSAGES
- COOLER TEMPERATURES THROUGH WEDNESDAY.
- UNSETTLED CONDITIONS THROUGH TUESDAY WITH PERIODS OF RAIN AND
SNOW. LIGHT SNOW ACCUMULATIONS EXPECTED MOST AREAS, WITH 2 TO 4
INCHES IN THE SOUTHERN FOOTHILLS. 4 TO 8 INCHES EXPECTED IN THE
MOUNTAINS.
- WINDS INCREASE ON WEDNESDAY OVER THE WESTERN FOOTHILLS.
- STRONG WINDS EXPECTED ACROSS THE REGION ON THURSDAY. WINDS MAY
BE STRONGER THAN SUNDAYS WIND EVENT, ESPECIALLY FROM BILLING
WEST.
- LOTS OF UNCERTAINTY WITH THE LATE WEEK FORECAST, BUT AN
ATMOSPHERIC RIVER EVENT MAY BRING A PROLONGED PERIOD OF
RAIN/SNOW THROUGH THE WEEKEND.
DISCUSSION
THE REST OF TODAY THROUGH SUNDAY...
HIGHLITES: ADDED A WINTER WEATHER ADVISORY FROM GOLDEN VALLEY EAST
THROUGH THE PANHANDLE OF ROSEBUD COUNTY UNTIL 9PM. 1 TO 4 INCHES
OF SNOW (PER MT MESONET OBS) HAS FALLEN IN THIS AREA AND AN
ADDITIONAL 1 TO 2 INCHES IS POSSIBLE THROUGH EARLY EVENING. ALSO,
PUSHED BACK START OF THE BIGHORN MOUNTAINS/FOOTHILLS WINTER
WEATHER ADVISORY TO MIDNIGHT TONIGHT.
HI-RES MODELS DOING A BETTER JOB WITH CURRENT PRECIPITATION
SITUATION THAN THE GFS/ECMWF. CURRENT NBM AND GFS/ECMWF ARE TOO
HIGH WITH PRECIPITATION CHANCES OVER CENTRAL AND SOUTHERN PORTIONS
OF THE FORECAST AREA, AND NOT HIGH ENOUGH ALONG THE NORTHERN TIER
OF COUNTIES FROM WHEATLAND TO CUSTER. CLOUD COVER AND NORTHERLY
WINDS ARE ALSO HOLDING TEMPERATURES BELOW NBM GUIDANCE. MADE
ADJUSTMENTS TO THE NBM FORECAST TO ACCOUNT FOR THESE TRENDS. BAND
OF SNOW HAS SET UP ALONG THE MUSSELSHELL RIVER VALLEY EXTENDING
EAST THROUGH NORTHERN ROSEBUD COUNTY TO JUST NORTH OF MILES CITY.
REPORTS OF LOCALLY MODERATE SNOWFALL WITH "BIG FLAKES" WITHIN THE
MOST INTENSE RADAR RETURNS. LATEST MT MESONET OBS SHOW 1 TO 4
INCHES HAS FALLEN SO FAR WITH ROADS ON WEBCAMS LOOKING SNOW
COVERED AND SLICK. ISSUED A WINTER WEATHER ADVISORY TO ACCOUNT FOR
THIS PERSISTEN SNOW BANDING.
THIS ACTIVITY IS A COMBINATION OF ISENTROPIC ASCENT, WHERE COLDER
AIR HAS DEEPENED ENOUGH, PACIFIC MOISTURE, AND JET LEVEL DYNAMICS.
ZONAL JET STREAM OVER THE AREA HAS A COUPLE OF JET MAXIMUMS
ASSOCIATED WITH IT AND THE ENTRANCE/EXIT REGION DYNAMICS
INTERACTING BETWEEN THESE FEATURES IS PRODUCING LIFT/SUBSIDENCE IN
SPOTS AS WELL AS SLOSHING THE COLDER AIR AROUND NEAR THE SURFACE.
MODELS GENERALLY HOLD THE MEAN JET POSITION RIGHT OVER OUR AREA
WHICH MEANS THE COLD AIR, WHILE IT MAY SLOSH AROUND A LITTLE,
ISN'T GOING TO HEAD SOUTHWARD MUCH MORE. DAYTIME WARMING OVER THE
NEXT HOUR OR TWO WILL ERODE OUT THE COLD AIR FROM THE WESTERN
FOOTHILLS AND ALLOW WESTERLY WINDS TO DEVELOP AND SPREAD EAST INTO
CENTRAL ZONES. THIS WILL FURTHER ERODE THE COLDER AIR OVER
CENTRAL AND EASTERN ZONES WHICH WILL WEAKEN THE ISENTROPIC LIFT
AND DIMINISH THE MORE WIDESPREAD PRECIPITATION THIS AFTERNOON INTO
THE EVENING HOURS. IN ITS PLACE MORE ISOLATED TO SCATTERED
RAIN/SNOW SHOWERS WILL PREVAIL THIS AFTERNOON INTO THE EVENING.
OVERNIGHT TONIGHT THE NEXT JET IMPULSE DIGS A BIT FURTHER SOUTH
AND ADDS SOME CYCLONIC CURVATURE WHICH WILL INCREASE LIFT
ACROSS MAINLY THE SOUTHERN HALF OF THE FORECAST AREA OVERNIGHT
THROUGH THE DAY ON TUESDAY. THIS SHOULD ALLOW COLDER AIR TO MOVE
SOUTHWARD WITH UPSLOPE HELPING TO INCREASE SNOWFALL OVER THE
SOUTHERN TIER OF ZONES. LATEST FORECAST SHOWS 50 TO 70 PERCENT
CHANCE FOR 2+ INCHES FOR THE BEARTOOTH AND SHERIDAN FOOTHILLS,
WITH A 30 TO 40 PERCENT CHANCE FOR 4+ INCHES THROUGH TUESDAY
EVENING. ONLY CHANGE MADE TO THE GOING WINTER HIGHLITES WAS TO
PUSH START TIME FOR THE CURRENT ADVISORY BACK TO MIDNIGHT TONIGHT.
AT THIS TIME DON'T PLAN TO ADD TO THE ADVISORY FOOTPRINT. WE HAVE
BEEN ADVERTISING PRETTY GOOD CHANCES FOR CENTRAL AND WESTERN ZONES
TO PICK UP A QUARTER OF AN INCH OF PRECIPITATION OR MORE WITH THIS
SYSTEM THROUGH TUESDAY NIGHT. THAT HAS DROPPED TO AROUND A 40%
CHANCE FOR THE FOOTHILLS, AND 10 TO 30 PERCENT FOR THE LOWER
ELEVATIONS. SO, OVERALL THIS SYSTEM HAS TRENDED DRIER FOR MOST
AREAS (OUTSIDE OF THE NORTHERN TIER THIS MORNING) DUE TO THE
STRONG ZONAL JET OVER THE AREA INTO TONIGHT.
ONCE THIS SYSTEM WRAPS UP TUESDAY NIGHT THE JET STREAM BACKS
NORTHWARD AND STRAIGHTENS OUT ONCE AGAIN. THIS PUSHES THE COLDER
AIR NORTHWARD AND WILL ALLOW FOR BETTER MIXDOWN OF THE WESTERN
WINDS ALOFT DUE TO WARMER SURFACE TEMPERATURES (UPPER 40S TO MID
50S) WEDNESDAY AFTERNOON. STRONGEST WINDS WILL BE IN THE WESTERN
FOOTHILLS, PARTICULARLY IN THE GAP PRONE AREAS AS SURFACE
PRESSURES FALL LEE OF THE DIVIDE. MAY NEED WIND HIGHLITES FOR
LIVINGSTON AS EARLY AS WEDNESDAY AFTERNOON.
WINDS CONTINUE TO INCREASE WEDNESDAY NIGHT AS A 155KT PACIFIC
JET STREAM TAKES AIM ON THE AREA. BY SUNRISE THURSDAY WE MAY BE
LOOKING AT WIND GUSTS OF 60+ MPH ACROSS THE WESTERN FOOTHILLS
DEPENDING ON THE TIMING AND ORIENTATION OF THE JET. THAT SAID,
WEDNESDAY NIGHT LOOKS BREEZY TO WINDY AND WARM OVER THE WESTERN
HALF OF THE FORECAST AREA (ROSEBUD COUNTY WEST).
THURSDAY IS SHAPING UP SIMILAR IF NOT A BIT STRONGER THAN THE WIND
EVENT WE HAD ON SUNDAY. THE STRENGTH OF THE WINDS IN THE
ATMOSPHERE OVER THE AREA ARE 10 TO 20KTS STRONGER THAN SUNDAY.
ALREADY MESSAGING THE STRONG WIND POTENTIAL IN DISCUSSIONS, SOCIAL
MEDIA, AND TARGETED EMAILS. WILL CONTINUE TO ADD TO THIS MESSAGING
AS THE EVENT UNFOLDS OVER THE NEXT COUPLE OF DAYS. MAIN MESSAGE,
IF YOU HAD WIND IMPACTS ON SUNDAY (GUSTS WERE 50 TO 90 MPH),
THURSDAY MAY PRODUCE BIGGER IMPACTS WITH STRONGER GUSTS.
ANOTHER KEY DIFFERENCE WITH THIS JET STREAM INTRUSION ON THURSDAY
IS THE PACIFIC MOISTURE TAP ASSOCIATED WITH IT. THIS IS A TRUE
ATMOSPHERIC RIVER EVENT. MEAN WATER VAPOR TRANSPORT LEVELS ARE 5
TO 6 SD ABOVE NORMAL WITH PWATS AROUND 2 SD ABOVE NORMAL. THIS
MOISTURE FETCH LOOKS TO BE ENOUGH TO OVERCOME THE INCREDIBLE
AMOUNT OF DOWNSLOPE THAT IS BEING FORECAST, SO IN THE MIDST OF A
STRONG WIND EVENT WE DO HAVE 30 TO 70% PRECIPITATION CHANCES IN
PLACE THURSDAY AFTERNOON. WILL BE KEEPING A CLOSE EYE ON FIRE
DANGERS FOR THURSDAY GIVEN THE WINDS, BUT THIS MOISTURE FETCH MAY
KNOCK THE FIRE THREAT DOWN A FEW NOTCHES BELOW CRITICAL.
FROM FRIDAY THROUGH NEXT WEEKEND PRECIPITATION CHANCES LOOK SOLID
ACROSS THE AREA WITH THE NBM SHOWING 30 TO 60 PERCENT CHANCES FOR
AN INCH PLUS OF PRECIPITATION THROUGH SUNDAY FOR CENTRAL AND
WESTERN ZONES, AND PRETTY MUCH EVERYONE OVER 50 PERCENT FOR HALF
AN INCH OR MORE. NBM GUIDANCE IS SHOWING PROBABILITIES OF 30 TO
60% FOR GREATER THAN 6 INCHES OF SNOWFALL THROUGH THE WEEKEND FOR
CENTRAL AND WESTERN ZONES, TAPERING OFF TO AROUND 20 PERCENT FOR
SOUTHEAST MONTANA. SNOW IS COMPLICATED BY VERY WIDE TEMPERATURE
SPREADS FRI/SAT. FOR INSTANCE THE REASONABLE RANGE FOR HIGH
TEMPERATURES IN BILLINGS ON FRIDAY IS 71 TO 35 AND 63 TO 28 FOR
SATURDAY. THIS REFLECTS THE UNCERTAINTY WITH THE LOCATION OF THE
JET STREAM AXIS. JUST A FEW HUNDRED MILES DIFFERENCE NORTH TO
SOUTH WILL MAKE A BIG DIFFERENCE IN WHERE THE COLD AIR IS LOCATED.
SO, STILL A LOT OF UNCERTAINTY IN THE EXTENDED FORECAST PAST THE
VERY WINDY THURSDAY PERIOD. STAY TUNED TO THE FORECAST THIS WEEK
IF YOU HAVE OUTDOOR OR TRAVEL PLANS HEADING INTO NEXT WEEKEND.
CHAMBERS
AVIATION
SCATTERED LIGHT SNOW SHOWERS TONIGHT WILL BRING AREAS OF MVFR
CIGS/VSBY (MAINLY WEST AND SOUTH OF KMLS), WHILE MOUNTAINS ARE
FREQUENTLY OBSCURED. BY EARLY TUESDAY, EXPECT SNOW TO BECOME MORE
IMPACTFUL OVER THE SOUTHERN MOUNTAINS AND FOOTHILLS, WITH MVFR AND
LOCAL IFR. TAF SITE MOST LIKELY TO SEE POOR FLYING WEATHER IS
KSHR. MOUNTAINS WILL BE MOSTLY OBSCURED. EXPECT SNOW TO TAPER TO
LIGHT SNOW SHOWERS LATE TUESDAY AFTERNOON. WINDS WILL NOT BE A
FACTOR THROUGH THE PERIOD. JKL
PRELIMINARY POINT TEMP/POPS
TUE WED THU FRI SAT SUN MON
-----------------------------------------------------------
BIL 028/042 022/049 037/062 037/055 032/048 019/036 026/050
45/S 30/N 33/R 76/W 68/W 63/J 54/W
LVM 024/038 018/047 039/056 044/057 043/053 026/044 033/054
35/S 10/N 34/R 55/W 58/W 54/J 44/W
HDN 027/042 020/050 033/062 032/055 028/047 017/037 024/049
55/S 40/B 45/R 86/W 78/W 73/J 44/W
MLS 027/041 023/045 031/051 027/041 026/034 014/029 017/039
22/S 10/B 47/O 78/W 68/J 52/J 33/J
4BQ 028/038 023/045 029/058 030/051 029/047 015/033 021/044
36/S 20/U 25/O 76/W 57/W 72/J 33/J
BHK 023/039 018/042 026/047 024/040 023/035 011/026 012/038
32/S 10/U 37/O 58/J 68/J 62/J 22/J
SHR 023/036 015/045 027/059 029/058 031/055 016/037 021/049
67/S 60/U 13/R 74/W 47/W 73/J 33/W
BYZ WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY IN EFFECT UNTIL 9 PM MDT THIS EVENING
FOR ZONES 29-31-42.
WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 8
AM MDT WEDNESDAY FOR ZONE 138.
WY...WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 8
AM MDT WEDNESDAY FOR ZONES 198-199.
WEATHER.GOV/BILLINGS
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